A printed circuit board is produced, for example, by a process of laminating a metal foil (such as a copper foil) layer as a conductive layer, on an insulating substrate, and etching the metal foil for removing unnecessary portions so as to form a patterned circuit. As a material for the insulating substrate, a fluororesin film excellent in dielectric properties or a polyimide film excellent in heat resistance is known.
Further, Patent Document 1 proposes a thermoplastic liquid crystal polymer film having a low dielectric constant and being suitable as an insulating substrate.